The present invention, in some embodiments thereof, relates to three dimensional (3D) printing with layers of powdered material and, more particularly, but not exclusively, to 3D printing of metal objects with powdered metal as the building material.
A number of different processes for fabricating solid objects by 3D printing with successive layers of powdered material are known. Some known 3D printing techniques selectively apply a liquid binder material based on a 3D model of the object, binding the material together layer by layer to create a solid structure. In some processes, the object is heated and/or sintered to further strengthen bonding of the material at the end of the building process.
Selective Laser Sintering (SLS) uses a laser as the power source to sinter layers of powdered material. The laser is controlled to aim at points in space defined by a 3D model, binding the material together layer by layer to create a solid structure. Selective laser melting (SLM) is comparable technique that applies full melting of the material instead of sintering. SLM is typically applied when the melting temperature of the powder is uniform, e.g. when pure metal powders are used as the building material.
U.S. Pat. No. 4,247,508 entitled “MOLDING PROCESS”, the contents of which are incorporated herein by reference, describes a molding process for forming a 3D article in layers. In one embodiment, planar layers of material are sequentially deposited. In each layer, prior to the deposition of the next layer, a portion of its area is solidified to define that portion of the article in that layer. Selective solidification of each layer may be accomplished by using heat and a selected mask or by using a controlled heat scanning process. Instead of using a laser to selectively fuse each layer, a separate mask for each layer and a heat source may be employed. The mask is placed over its associated layer and a heat source located above the mask. Heat passing through the opening of the mask will fuse together the particles exposed through the opening of the mask. The particles not exposed to the direct heat will not be fused.
U.S. Pat. No. 5,076,869 entitled “MULTIPLE MATERIAL SYSTEMS FOR SELECTIVE BEAM SINTERING”, the contents of which are incorporated herein by reference, describes a method and apparatus for selectively sintering a layer of powder to produce a part comprising a plurality of sintered layers. The apparatus includes a computer controlling a laser to direct the laser energy onto the powder to produce a sintered mass. For each cross-section, the aim of the laser beam is scanned over a layer of powder and the beam is switched on to sinter only the powder within the boundaries of the cross-section. Powder is applied and successive layers sintered until a completed part is formed. Preferably, the powder comprises a plurality of materials having different dissociation or bonding temperatures. The powder preferably comprises blended or coated materials.
International Patent Publication No. WO2015/170330 entitled “METHOD AND APPARATUS FOR 3D PRINTING BY SELECTIVE SINTERING”, the contents of which are incorporated herein by reference, discloses a method for forming an object by 3D printing that includes providing a layer of powder on a building tray, performing die compaction on the layer, sintering the layer that is die compacted by selective laser sintering or selective laser melting and repeating the providing, the die compaction and the sintering per layer until the three dimensional object is completed. The selective sintering disclosed is by a mask pattern that defines a negative of a portion of the layer to be sintered.